A member of the Counter Terrorism Centre (TEK) patrols the area in front of the Parliament in downtown Budapest, Hungary, Tuesday, March 22, 2016. Hungary raised its terrorism awareness level to grade 2 after a series of attacks in Brussels. (Zoltan Balogh/MTI via AP)Zoltan Balogh

Terrorists may have been planning to detonate nuclear bomb

Isis-linked terrorists in Belgium are thought to have been planning to build a 'dirty' nuclear bomb, according to several reports.

Concerns over security at nuclear plants have led to 11 workers having their passes revoked, The Times reported.

A senior Belgian nuclear official was also secretly monitored by suspects linked to the 13 November Paris attacks, La Derniere Heure newspaper reported earlier this year. Late last year, police in Belgium seized surveillance footage of the high-ranking nuclear official, which showed him entering and leaving his home, during a raid on terrorist suspects.

An official at Belgium's Federal Agency for Nuclear Control told The Times: "When you start filming someone in the way they did, the logical conclusion is that they wanted to abduct that person and to obtain radioactive material."

The passes of 11 staff at the Tihange nuclear power station have been withdrawn after they were vetted by a committee including intelligence and security agencies.

A dirty bomb is easier to make than a nuclear bomb but does not create a fission explosion. Instead, traditional explosives are used to spread radioactive material over an area, potentially contaminating it for years.

The risk to health is relatively small with some experts saying more could be killed in the panic created by such an attack than the radiation itself.